Rabu, 24 Desember 2008

Clue' to sexes' pain difference

US researchers found brain differences affecting the potency of opioids such as morphine.

The Journal of Neuroscience study also found drug effectiveness varied during the rats' menstrual cycles.

Another expert said it showed the growing importance of tailoring pain relief to match the individual needs of the patient.

Morphine remains one of the most widely used drugs to alleviate severe persistent pain and doctors have noticed that it frequently does not work as well in women.

However, the study from Georgia State University claims to be the first to pinpoint the reason why.

It looked closely at a tiny area of the brain called the periaqueductal grey area (PAG), which is important in the way that pain signals are interpreted.

Many neurons in this region have, on their surface, "receptors" designed to receive and lock onto the molecules found in opioid drugs.

These "mu-opioid receptors", when locked onto an opioid drug, send a message telling the brain to stop responding to pain signals, reducing the sensation of pain.

The Georgia State team found that, in the rat brain, females had a lower level of mu-opioid receptors in this part of the brain, suggesting that the potential potency of morphine is much reduced.

Additional tests suggested that the response to morphine varied depending on which part of the menstrual cycle the female rat was in.

Better treatment

Professor Anne Murphy, who led the research, said: "It is increasingly clear that morphine is significantly less potent in women compared with men - until now, the mechanism driving the phenomenon was unknown.

"Additional research with the inclusion of female subjects needs to be devoted to determining a more potent treatment for persistent pain in women."

Professor Karen Berkley, from Florida State University, described the research as "important" and called for more attention to be paid to make sure that women received adequate pain relief.

"What this research is trying to do is understand the hormonal influences on pain in women.

"Clinicians are becoming far more aware of this issue, certainly more than they were five or six years ago."

Human trials, already under way, would need to be concluded to confirm the results of this study, she said.


Argentina investigates ex-leader

Nestor Kirchner
Nestor Kirchner was succeeded as president by his wife

Former Argentine President Nestor Kirchner is to be investigated by a court over corruption allegations.

A senior judge said the probe would also look at certain aspects of Mr Kirchner's links with the Venezuelan President, Hugo Chavez.

Mr Kirchner, who has made no comment, is married to current President Cristina Fernandez de Kirchner.

The investigation was launched at the request of opposition leader and former presidential candidate Elisa Carrio.

Prosecutors said the evidence submitted by her was sufficient to warrant a judicial inquiry.

Venezuela contract

The allegations against Mr Kirchner and two former government ministers centre on 30 alleged cases of corruption dating back to his presidency, which ended last year.

Ms Carrio alleges the former president and several top government officials distributed big construction contracts and government-owned licenses to drill for oil in return for financial rewards.

The investigation will also examine a contract signed in 2004 by Mr Kirchner and his Venezuelan counterpart.

Elisa Carrio
Elisa Carrio stood against President Cristina Fernandez de Kirchner

Under the terms of the agreement, Argentina was to buy Venezuelan fuel and in return Venezuela would purchase Argentine manufactured goods.

It is alleged that $90m (£61m) in Argentine government funds used to complete to deal have disappeared without a trace.

The BBC's Greg Morsbach says this is not the first time Argentina's relationship with Venezuela has come under close scrutiny.

A court in the US recently jailed two Venezuelan businessmen for illegally acting as agents of the Venezuelan government on US soil in an effort to silence a man who smuggled a suitcase filled with $800,000 in cash into Argentina.

US prosecutors say the cash was sent by Caracas to fund the presidential election campaign of Mrs Fernandez de Kirchner.

The Venezuelan and Argentine governments have rejected the allegations, saying the trial was politically motivated.

A Uruguayan has also been jailed for his involvement in the case.